Digital communication system, transmitter, and data selector

ABSTRACT

A digital communication system comprises a transmitter for sequentially transmitting predetermined format data; and a plurality of receivers  102  each including a data selecting apparatus  104  for selecting required data from received data group and outputting selected data. The transmitter transmits data to the receivers in one of a first transmission mode having group destination directing information indicating that the data is to be transmitted to a receiving group consisting of predetermined receivers of the plurality of receivers, group specifying information for specifying a receiving group of receiving groups to which the data is to be transmitted, and in-group identification information for identifying a receiver in an arbitrary receiving group to which the data is to be transmitted, a second transmission mode having the group destination directing information and the group specifying information are included in the data, and a third transmission mode having the group destination directing information.

This application is the U.S. national stage of PCT/JP98/01417, filedMar. 27, 1998.

TECHNICAL FIELD

The present invention relates to a digital communication system, atransmitter, and a data selecting apparatus and, more particularly to adigital communication system, a transmitter, and a data selectingapparatus, in which data is transmitted to many receiver groups for eachreceiver or for each receiving group comprising specified receivers.

BACKGROUND ART

In recent years, in many cases, video data, audio data or other data istransmitted or stored in the form of digital data. In such cases, thesedata is generally divided into data such as packets having a datastructure comprising plural fields, to be transmitted or stored. Also,in some cases, plural pieces of data is made into a packet, and thenpackets are multiplexed to be transmitted through a transmission mediumor to be stored in a storage medium. MPEG system standard is a standardfor a data structure and multiplexing for this case, and data istransmitted or stored by a method according to a packet data structureaccording to this standard.

Conventionally, in a system in which such packet data is multiplexed,equipment which receives data is adapted to select data to-be-receivedfrom the multiplexed packet data. By way of example, a method fortransmitting data to each receiver and selecting data in each receiverin digital broadcasting using a data multiplexing method according toMPEG system standard will now be briefly described in brief.

In digital broadcasting, when key information used for decryptingencrypted video or audio data or an electric mail is transmitted, it issometimes necessary that data ((hereinafter referred to as “EMM”(Entitlement Management message) data) be transmitted to specifiedreceivers individually. In this case, a data structure termed “section”defined in MPEG system standard is employed. The section data used fortransmitting the EMM data, comprises a field of “table identifier”indicating that type of corresponding data is the EMM data, a fieldindicating the number of a destination receiver, and a field whichcontains data to-be-transmitted.

The receiver which receives such data is provided with a data selectingapparatus for selecting required data. The data selecting apparatuscontains the table identifier indicating the EMM data and a receivernumber inherent to the receiver.

When the receiver receives the section data, the table identifier istaken out of the received data to check whether this indicates the EMMdata. When this indicates the EMM data, a field of the receiver numberis taken out of the received data to check whether this matches thereceiver number inherent to the receiver. When a match is found betweenthem, the data selecting apparatus selects and outputs this sectiondata, whereby only data for the receiver can be selected.

By the way, recently, in order to send a variety of information withflexibility and only to desired receivers, it is required that receiversbe grouped and data be sent to each group besides sending information toreceivers individually. It is also required that the same data be sentto all the receivers simultaneously. Further, it is necessary to selectreceivers being specially served under a receiving contract and senddata only to these receivers simultaneously.

However, in the transmission method of the EMM data and the dataselecting method according to a prior art, since the datato-be-transmitted has a structure in which the information indicatingthe EMM data is stored in the table identifier field, and the number ofthe destination receiver is stored in the receiver number field, at thereceiver side, whenever the table identifier field indicates the EMMdata, it is checked whether the value of the receiver number fieldmatches the receiver number of itself, and only when there is a matchbetween them, the EMM data is selected and received.

With a data structure in which a receiver has a receiver number uniquelydetermined for each receiver, data is sent to only one receiverspecified by a transmission end, and it is therefore impossible tosimultaneously send data to a receiver group comprising plural receiversor on a contract broadcasting service basis. Hence, when individual datais sent for the receiver group or on the broadcasting service basis, itis necessary to specify receivers one by one and sequentially send thedata to them. So, one transmission end requires several hundredsthousand to several millions of receivers, and accordingly, the methodin which the data is sequentially sent to the receivers specified one byone, requires enormous data transmission bandwidth for flexible datatransmission to the receivers. With a restricted data transmissionbandwidth for broadcasting, flexible data transmission adapted tovarious services or in response to users' demands is not realized, andthereby quality of service is degraded.

In Japanese Published Patent Application (No. Hei. 7-143117), there isdisclosed a communication terminal in which a service group numberstored in a receiver which has a right to receive a program is comparedto a service group number specified in transmitted program data and whena match is found between them, the program is received.

In this communication terminal, when information destined for anindividual ID is received, detection of match of service type numbers isfirst conducted, and decision on match of the individual ID is thenconducted, which increases the amount of processing required fordeciding whether the information destined for the individual ID can bereceived.

The present invention is conceived in view of the background art, and anobject of the present invention is to provide a digital communicationsystem in which data is simultaneously sent to all receivers or aprescribed receiver group, as well as to specified receivers, and atransmitter and a data selecting apparatus used in this system.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention, there is provided adigital communication system comprising: a transmitter for sequentiallytransmitting predetermined format data; and a plurality of receiverseach including a data selecting apparatus for selecting required datafrom received data group and outputting selected data, wherein thetransmitter transmits data to the receivers in one of a firsttransmission mode in which group destination directing informationindicating that the data is to be transmitted to a receiving groupconsisting of predetermined receivers of the plurality of receivers,group specifying information for specifying a receiving group ofreceiving groups to which the data is to be transmitted, and in-groupidentification information for identifying a receiver in an arbitraryreceiving group to which the data is to be transmitted, are included inthe data, a second transmission mode in which the group destinationdirecting information and the group specifying information are includedin the data, and a third transmission mode in which the groupdestination directing information is included in the data.

According to another embodiment of the present invention, in the digitalcommunication system of the earlier embodiment, the transmitter includesdata structuring means for structuring data to be transmitted, and thedata selecting apparatus includes: parameter storage means forprestoring plural parameters which are to be compared to the groupdestination directing information, the in-group identificationinformation, and the group specifying information; correspondencepattern detecting means for comparing the information stored in the datato the parameters, respectively, to detect correspondence patterns; andoutput means for selecting the required data according to thecorrespondence patterns detected by the correspondence pattern detectingmeans and outputting the selected data.

According to another embodiment of the present invention, in the digitalcommunication system of the above embodiment, the group destinationdirecting information includes a group destination number indicatingthat the data to be transmitted is destined for a group when the data tobe transmitted is destined for the group, the group destinationdirecting information includes a specified receiver destination numberindicating that the data to be transmitted is destined for a specifiedreceiver when the data to be transmitted is destined for the specifiedreceiver, the parameter storage means prestores a first parameter to becompared to the group destination number, a second parameter to becompared to the specified receiver destination number and the in-groupidentification information, and a third parameter to be compared to thegroup specifying information, the correspondence pattern detecting meansdetects one of first and second correspondence patterns in such a waythat the first correspondence pattern is detected when the specifiedreceiver destination number and the in-group identification informationmatch the second parameter and the group specifying information matchesthe third parameter in the first transmission mode, and the secondcorrespondence pattern is detected when the group destination numbermatches the first parameter and the group specifying information matchesthe third parameter in the second transmission mode, and the outputmeans selects the required data according to one of the first and secondcorrespondence patterns and outputs the selected data.

According to another embodiment of the present invention, in the digitalcommunication system of the above embodiment, the group destinationdirecting information includes a number for specifying all receiverswhen the data to be transmitted is destined for the all receivers, theparameter storage means prestores a fourth parameter to be compared tothe number for specifying all receivers, the correspondence patterndetecting means detects a third correspondence pattern when the numberfor specifying all receivers matches the fourth parameter in the thirdtransmission mode, and the output means selects the required dataaccording to the third correspondence pattern and outputs the selecteddata.

According to another embodiment of the present invention, in the digitalcommunication system of the above embodiment, the group destinationdirecting information includes a special group number when the data tobe transmitted is destined for all receivers which belong to a specialgroup, when the data to be transmitted is destined for all receiverswhich belong to the special group, the parameter storage means prestoresa fourth parameter to be compared to the special group number, thecorrespondence pattern detecting means detects a fourth correspondencepattern when the special group number matches the fourth parameter inthe third transmission mode, and the output means selects the requireddata according to the fourth correspondence pattern and outputs theselected data.

In the digital communication system so constructed, data can betransmitted to a specified receiver, a predetermined receiving group,all receivers, or all receivers which belong to a special group, andselection of data in the receiver is performed with a small-scalecircuit.

According to another embodiment of the present invention, there isprovided a transmitter which is used in a digital communication systemwherein data is structured to be in a predetermined format and istransmitted to a plurality of receivers, including: data structuringmeans for structuring data to be transmitted in one of a first datatransmission mode in which group destination directing informationindicating that the data is to be transmitted to a receiving groupconsisting of predetermined receivers of the plurality of receivers,group specifying information for specifying a receiving group ofreceiving groups to which the data is to be transmitted, and in-groupidentification information for identifying a receiver in an arbitraryreceiving group to which the data is to be transmitted, are included inthe data, a second data transmission mode in which the group destinationdirecting information and the group specifying information are includedin the data, and a third data transmission mode in which the groupdestination directing information is included in the data.

According to another embodiment of the present invention, in thetransmitter of the above embodiment the group destination directinginformation in the first transmission mode includes a specified receiverdestination number indicating that the data to be transmitted isdestined for a specified receiver when the data to be transmitted isdestined for the specified receiver.

According to another embodiment of the present invention, in thetransmitter of an above embodiment, the group destination directinginformation in the second transmission mode includes a group destinationnumber indicating that the data to be transmitted is destined for agroup, when the data to be transmitted is destined for the group.

According to another embodiment of the present invention, in thetransmitter of an above embodiment, the group destination directinginformation in the third transmission mode includes a number forspecifying all receivers indicating that the data to be transmitted isdestined for all receivers, when the data to be transmitted is destinedfor the all receivers.

According to another embodiment of the present invention, in thetransmitter of an above embodiment, the group destination directinginformation in the third transmission mode includes a special groupnumber indicating that the data to be transmitted is destined for allreceivers which belong to a special group, when the data to betransmitted is destined for the all receivers which belong to thespecial group.

According to another embodiment of the present invention, there isprovided a data selecting apparatus built in a receiver in a digitalcommunication system, which is supplied with predetermined format dataas inputs and selects required data from input data group and outputsselected data, and the apparatus comprises: parameter storage means forprestoring plural parameters which are to be compared to groupdestination directing information in the data indicating that the datato be transmitted is destined for a receiving group consisting ofpredetermined receivers of the plurality of receivers, group specifyinginformation in the data for specifying a receiving group of receivinggroups to which the data is to be transmitted, and in-groupidentification information in the data for identifying a receiver in anarbitrary receiving group to which the data is to be transmitted;correspondence pattern detecting means for comparing the informationstored in the data to the parameters, respectively, to detectcorrespondence patterns; and output means for selecting the requireddata according to the correspondence patterns detected by thecorrespondence pattern detecting means and outputting the selected data.

According to another embodiment of the present invention, in the dataselecting apparatus of the above embodiment, the group destinationdirecting information includes a group destination number indicatingthat the data to be transmitted is destined for a group when the data tobe transmitted is destined for the group, the group destinationdirecting information includes a specified receiver destination numberindicating that the data to be transmitted is destined for a specifiedreceiver when the data to be transmitted is destined for the specifiedreceiver, the parameter storage means prestores a first parameter to becompared to the group destination number, a second parameter to becompared to the specified receiver destination number and the in-groupidentification information, and a third parameter to be compared to thegroup specifying information, the correspondence pattern detecting meansdetects one of first and second correspondence patterns in such a waythat the first correspondence pattern is detected when the specifiedreceiver destination number and the in-group identification informationmatch the second parameter and the group specifying information matchesthe third parameter, and the second correspondence pattern is detectedwhen the group destination number matches the first parameter and thegroup specifying information matches the third parameter, and the outputmeans selects the required data according to one of the first and secondcorrespondence patterns and outputs the selected data.

In the data selecting apparatus so constructed, in the specifiedreceiver, predetermined receivers which belong to the specifiedreceiving group, all receivers, or the receivers which belong to thespecial group, selection of the transmitted data can be performed.Simultaneously, selection of the data in the receiver is performed witha small-scale circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a communication system according to anembodiment of the present invention.

FIG. 2 is a diagram showing a structure of data which is transmitted toa specified receiver of the embodiment.

FIG. 3 is a diagram showing a structure of data which is transmitted toa specified group of the embodiment.

FIG. 4 is a diagram showing a structure of data which is transmitted toall receivers of the embodiment.

FIG. 5 is a diagram showing a structure of data which is transmitted toa special group of the embodiment.

FIG. 6 is a diagram showing construction of a receiver in thecommunication system according to the embodiment of the presentinvention.

FIG. 7 is a diagram showing a data selecting apparatus in thecommunication system according to the embodiment of the presentinvention.

FIG. 8 is a diagram showing a data format of the embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, a preferred embodiment of the present invention will be described.

FIG. 1 illustrates a digital communication system 100 of the presentinvention. The communication system 100 comprises a transmitter 101, anda receiver 102 for receiving digital data transmitted from thetransmitter 101. The digital communication system 100 is a digitalbroadcasting system, for example, and comprises one transmitter 101 tomany receivers 102, the transmitter 101 being connected to each of thereceivers 102 through a communication network NW. Although thecommunication network NW is wire herein, it may be wireless.

In general, as a data format of data transmitted through the network NW,a “transport stream” defined in MPEG system standard is employed. Thetransport stream is a data format in which video or audio, programspecific information, EMM data, and so forth are multiplexed in packets.The transport stream is illustrated in FIG. 8. A transport stream 140 iscomposed of transport streampackets 141 of a fixed length. The transportstream packets 141 each comprises a header 141 a, an adaptation field141 b, and data part 141 c, and in the data part 141 c, video or audiodata and so forth are stored. The video or audio data is first stored ina data format illustrated as a PES packet 142, and then stored in thetransport stream packet 141. The program specific information or the EMMdata is first stored in data formats illustrated as section data, andthen stored in the transport stream packet 141. The PES packet 142comprises a header 142 a and a data part 142 b. PES packets aresometimes stored in plural transport stream packets. The section data143 comprises a header 143 a and a data part 143 b, and the section data144 comprises a header 144 a, a destination part 144 b, and a data part144 c and plural pieces of section data may be stored in a transportstream packet, or one section data may be stored in plural transportstream packets. The section data 144 which contains the EMM data, alsocontains destination information indicating a receiver by which the EMMdata is to be received.

The transmitter 101 comprises a data structuring unit 103. The datastructuring unit 103 is used for structuring data to-be-transmitted tobe in section data format according to MPEG system standard. Eachreceiver 102 includes a data selecting apparatus 104 for selecting data.The data selecting apparatus 104 comprises a parameter storage unit 105for storing four types of parameters, a correspondence pattern detectingunit 106 for receiving data and comparing the data to the parameterstored in the parameter storage unit 105 to detect a correspondencepattern of them, and an output unit 107 for selecting data according tothe correspondence pattern detected by the correspondence patterdetecting unit 106 and outputting selected data.

The parameters stored in the parameter storage unit 105 can be set by anIC card and the like provided by a transmitting end when the usersubscribes to the digital broadcasting system.

The present invention is characterized in that data is broadcast in anyof four manners below. That is, in the digital communication system 100,a signal transmitted from the transmitter 101 is:

(1) received only by a specified receiver 102;.

(2) received only by a specified receiving group comprising pluralreceivers 102;

(3) received by all receivers 102; or

(4) received by a specified special group.

This will now be described in detail.

FIGS. 2 through 5 illustrate a data structure of EMM data 108to-be-transmitted. Referring to these figures, these EMM data 108 isdata which has been structured by the data structuring unit 103 in thetransmitter 101, and be in a section data format according to MPEGsystem standard. The EMM data 108 comprises a table ID field 109, afirst field 110, and a second field 111.

The table ID field 109 is composed of 8 bits and indicates what type ofdata corresponding section data contains. In this embodiment, in thetable ID field 109, “84h” (hereinafter hexadecimal number is representedby “h” at its end) is stored. The “84h” indicates that the section datais the EMM data 108 transmitted to a specified receiver 102.

The first field 110 is composed of 16 bits and contains groupdestination directing information indicating that the EMM data 108 isdestined for a receiving group including a prescribed receiver 102 ofplural receivers, and indicating that which receiving group the EMM data108 is transmitted to. Further, in-group identification informationindicating that the EMM data 108 is destined for a specified receiver102 in an arbitrary group is stored in the first field 110 as necessary.

More specifically, in a case where the EMM data 108 is destined for thespecified receiver 102, to lower 1 byte of the receiver unique number asthe in-group identification information, a specified receiverdestination number “FFh” indicating that the EMM data 108 is destinedfor a specified receiver as the group destination directing informationis added, and the resulting number is set in the first field of the EMMdata 108 (see FIG. 2). For example, when a receiver unique number of 4bytes is “0 1 2 3 4 5 6 7h”, “FF67h” is set in the first field 110 ofthe EMM data 108. This means that a receiver 102 of a receiver uniquenumber whose lower 1 byte is “67h” in an arbitrary receiving group isspecified as destination. In this case, “an arbitrary receiving group”is not a specified one but is any of receiving groups. A receiving groupis specified by the group specifying information stored in the secondfield 111.

When the EMM data 108 is transmitted to a receiving group, a groupdestination number “0000h” is set as the group destination directinginformation (see FIG. 3). This indicates that the EMM data 108 isdestined for a receiving group comprising prescribed receivers of theplural receivers rather than individual receivers.

When the EMM data 108 is destined for all receivers 102, a number forspecifying all receivers “00001h” is set as the group destinationdirecting information (see FIG. 4).

When the EMM data 108 is destined for a special group, a special groupnumber “0002h” is set as the group destination directing information(see FIG. 5). This indicates that the EMM data 108 is transmitted to allreceivers 102 which belongs to a special group. It should be noted thatthe special receiving group comprises receivers 102 under a contract ofa special broadcasting service.

The second field 111 is composed of a part of data bytes of the EMM data108. In this embodiment, first 3 bytes of the data bytes are used. Inthe second field 111, the group specifying information for specifying areceiving group to which the EMM data 108 is to be transmitted isstored. When the EMM data 108 is destined for a specified receivinggroup, a group specifying number, for example, “012345h” is set as thegroup specifying information (see FIGS. 2 and 3). The group specifyingnumber “012345h” indicates that the EMM data 108 is transmitted to areceiver in a specified receiving group in which upper 3 bytes of thereceiver unique number corresponds to the group specifying number“012345h”.

As shown in FIG. 2, lower 1 byte of the receiver unique number as thein-group identification information and the group specifying number areset, resulting in the EMM data 108 for a receiver 102 specified by thein-group identification information in a receiving group specified bythe group specifying number. As shown in FIG. 3, the group destinationnumber “0000h” and the group specifying number “012345h” are set,resulting in the EMM data 108 for all receivers 102 which belong to areceiving group specified by the group specifying number. As shown inFIG. 4, the number specifying all receivers “0001h” is set, resulting inthe EMM data 108 for all receivers 102 irrespective of receiving groups.As shown in FIG. 5, a special group number “0002h” is set so that theEMM data 108 is destined for every receiver 102 in a special receivinggroup under a contract of special service. As shown in FIGS. 4 and 5, itis not necessary to set the group specifying information.

TABLE 1 shows setting for each broadcasting.

TABLE 1 Field Destination First field 110 Second field 111 IndividualFF00h + Receiver unique number Receiver Receiver unique number upper 3bytes lower 1 byte Receiving 0000h Receiver unique number Group (groupdestination number) upper 3 bytes All 0001h (number for — Receiversspecifying all receivers) Service 0002h (special group — Group number)

Subsequently, the receiver 102 will be described in detail. FIG. 6illustrates a construction of the receiver 102. Received broadcast data,for example, data modulated by QPSK (quadrature phase shift keying), isfirst demodulated by a digital demodulating circuit 121, and then apacket to-be-received is selected by a packet selecting circuit 122. Apacket which contains video or audio data is decrypted by a decryptingcircuit 126 when the packet has been encrypted and receiving of this isauthorized because key information for decrypting encryption is given.Then, the video or audio data is taken out of the packet by a packetprocessing circuit 123, and then temporarily stored in a buffer memory129 by a memory access circuit 127. Then the video and audio data aresent to a video and audio decoding circuit 128 at time when they are tobe reproduced and displayed, to be decompressed therein, and theresulting restored video and audio data is output as NTSC or PAL videosignals, to be displayed. From a packet which contains section data suchas the program specific information other than the EMM data, the sectiondata is taken out of by the packet processing circuit 123, and sent to asection processing circuit 124. In the section processing circuit 124,section data to-be-received other than the EMM data is selected by asection selecting circuit 125, and then sent to the memory accesscircuit 127, to be stored in the buffer memory 129. The section datastored in the buffer memory 129 is used by a CPU 120 for constructing aprogram table or a selecting a program for the receiver.

Meanwhile, a packet which contains the EMM data 108 is selected by thepacket processing circuit 123, and sent to the section processingcircuit 124. In the section processing circuit 124, the sectionselecting circuit 125 and a data selecting apparatus 104 performselection according to the information stored in respective fields 109,110, and 111 of the EMM data 108, and then send the EMM datato-be-received through the memory access circuit 127 to the buffermemory 129, to be stored therein. In a case where the EMM data stored inthe buffer memory 129 is information used for decrypting encrypted videoor audio data which can be received, the CPU 120 reads this and createskey information, and sets the key information in the decrypting circuit126, thereby allowing video or audio data to be decrypted. In a casewhere the EMM data received and stored in the buffer memory 129 is mailinformation, this is read by the CPU 120 in accordance with operation ofthe user, and then sent to the video and audio decoding circuit 128, tobe displayed.

FIG. 7 illustrates operation of the data selecting apparatus 104 shownin FIG. 6. Referring to FIGS. 1 and 7, the parameter storage unit 105 ofthe data selecting apparatus 104 (see FIG. 1) stores first to fourthparameters. In this embodiment, “0000h”, “FF67h” and “012345h” arestored as the first parameter 130, the second parameter 131, and thethird parameter 132, respectively. In addition, “0001h” and “0002h” arestored as the fourth parameters 133 and 134, respectively.

The correspondence pattern detecting unit 106 of the data selectingapparatus 104 (see FIG. 1) comprises a first detecting circuit 135, asecond detecting circuit 136, a third detecting circuit 137, and fourthdetecting circuits 138 and 139.

The first detecting circuit 135 compares the first parameter 130 “0000h”to the information stored in the first field 110 of the EMM data 108, todetect a match/mismatch between them, and when the match is found, thecircuit 135 outputs the input EMM data 108.

The second detecting circuit 136 compares the second parameter 131“FF67h” to the information stored in the first field 110 of the EMM data108, to detect a match/mismatch between them, and when the match isfound, the circuit 136 outputs the EMM data 108.

The third detecting circuit 137 compares the third parameter 132“012345h” to the information stored in the second field 111 of the EMMdata 108 output from the first detecting circuit 135 or the seconddetecting circuit 136, to detect a match/mismatch between them, and whenthe match is found, the circuit 137 outputs the input EMM data 108.

The fourth detecting circuit 138 compares the fourth parameter 133“0001h” to the information stored in the first field 110 of the receivedEMM data 108, to detect a match/mismatch between them, and when thematch is found, the circuit 138 outputs the input EMM data 108. Thefourth detecting circuit 139 compares the fourth parameter 134 “0002h,”to the information stored in the first field 110 of the received EMMdata 108, to detect a match/mismatch between them, and when the match isfound, the circuit 139 outputs the input EMM data 108.

In other words, the first to fourth detecting circuits 135 to 139 filterthe input. EMM data 108. When the EMM data is output from at least oneof the third and fourth detecting circuits 137, and 138 and 139, theoutput unit 107 outputs the EMM data 108. As a result, a receiver 102can receive only EMM data 108 which specifies itself as destination.

Although the fourth detecting circuits 138 and 139 are shown as beingseparate in FIG. 7 in order to explain operation of the data selectingapparatus 104, they may be configured by the same circuit.

More specifically, the following operation is performed in this dataselecting apparatus 104.

The EMM data 108 is input to the first, second, and fourth detectingcircuits 135, 136, 138, and 139. The first detecting circuit 135 checkswhether there is a match between the information stored in the firstfield 110 and the first parameter 130 “0000h”, and when there is thematch between them (a correspondence pattern is detected), the EMM data108 passes through the first detecting circuit 135. The second detectingcircuit 136 checks whether there is a match between the informationstored in the first field 110 and the second parameter 131 “FF67h”, andwhen there is the match between them, the EMM data 108 passes throughthe second detecting circuit 136.

The EMM data 108 which has passed through the first detecting circuit135 or the second detecting circuit 136 is input to the third detectingcircuit 137, which checks whether there is a match between theinformation stored in the second field 111 and the third parameter 132“012345h”, and when there is the match between them, the EMM data 108passes through the third detecting circuit 137. The output unit 107outputs the EMM data 108 which has passed through these circuits 135,136, and 137.

The fourth detecting circuit 138 compares the information stored in thefirst field 110 to the fourth parameter 133 “0001h”, and when there isthe match between them, the EMM data 108 passes through the fourthdetecting circuit 138. The fourth detecting circuit 139 compares theinformation stored in the first field 110 of the EMM data 108 and thefourth parameter 134 “0002h”, and when there is the match between them,the EMM data 108 passes through the fourth detecting circuit 139. Theoutput unit 107 outputs the EMM data 108 which has passed through thefourth detecting circuit 138 or 139.

Substantially, broadcasting in the communication system 100 will bedescribed.

First, in the transmitter (see FIG. 1), the data structuring unit 103for the EMM data structures the EMM data 108 to be in one of the formatsshown in FIGS. 2 to 5 and transmits the same to the receiver 102, wherethe EMM data 108 is selected as described below.

(1) Broadcasting for Specified Receiver

Assume that “01234567h” is set as the number of a specified receiver102. Upper 3 bytes “012345h” of 4 bytes “01234567h” indicate a receivinggroup to which the specified receiver 102 belongs, and lower 1 byte“67h” indicates the number in the receiving group. Therefore, thereceiver unique number “FF67h” and the group specifying number “012345h”are set in the first field 110 and the second field 111 of the EMM data108 (see FIG. 2), respectively. Also assume that the second parameter131 “FF67h”, and the third parameter 132 “012345h” are respectively setin the parameter storage unit 105 of the data selecting apparatus 104 ofone of the plural receivers 102.

The EMM data 108 is subjected to predetermined processing in the digitaldemodulating circuit 121, the packet selecting circuit 122, and thepacket processing circuit 123, and is input to the section processingcircuit 124, where the table ID field 109 of the EMM data 108 is checkedby the section selecting circuit 125, and it is decided that this is EMMdata when “84h”. Then, the EMM data 108 is input to the data selectingapparatus 104. In this embodiment, since “84h” is stored in the table IDfield 109, the EMM data 108 is input to the data selecting apparatus104.

When the EMM data 108 is input to the data selecting apparatus 104, theinformation stored in the first field 110 is compared to the firstparameter 130, the second parameter 131, and the fourth parameters 133and 134 as already described with reference to FIG. 7. Since thereceiver unique number “FF67h” and the group specifying number “012345h”are set in the first field 110 and the second field 111 of the EMM data108, respectively, the “FF67h” matches the second parameter 131 of thereceiver 102, so that the EMM data 108 passes through the seconddetecting circuit 136. Then, the group specifying number “012345h” ofthe second field 111 matches the third parameter 132 of the receiver102, so that the EMM data 108 passes through the third detecting circuit137 to the output unit 107, which outputs the EMM data 108.

As thus described, broadcasting for the specified receiver 102, amongmany receivers 102, can be provided. On the other hand, in a case whereanother number is set in a storage position of the receiver uniquenumber or the group specifying number, since it is different from thesecond parameter 131 or the third parameter 132, the EMM data 108 willnot be output from the output unit 107.

(2) Broadcasting for Specified Receiving Group

Assume that “012345h” is set in receivers 102 which belong to aspecified group, as the number indicating a receiving group to whichthey belong. Therefore, the group destination number “0000h” and thegroup specifying number “012345h” are set in the first field 110 and thesecond field 111 of the EMM data 108 (see FIG. 3), respectively. Alsoassume that the first parameter 130 “0000h”, and the third parameter 132“012345h” are respectively set in the parameter storage unit 105 of thedata selecting apparatus 104 of each of the receivers 102 in thereceiving group.

When the EMM data 108 is input to the data selecting apparatus 104, theinformation stored in the first field 110 is compared to the firstparameter 130, the second parameter 131, and the fourth parameters 133and 134 as already described with reference to FIG. 7. Since the groupdestination number “0000h” and the group specifying number “012345h” areset in the first field 110 and the second field 111 of the EMM data 108,respectively, the “0000h” matches the first parameter 130 of thereceiver 102, so that the EMM data 108 passes through the firstdetecting circuit 135. Then, the group specifying number “012345h” inthe second field 111 of the EMM data 108 matches the third parameter 132of the receiver 102, so that the EMM data 108 passes through the thirddetecting circuit 137 to the output unit 107, which outputs the EMM data108. This operation is performed by all receivers 102 in the receivinggroup.

As thus described, broadcasting for all receivers 102 in the receivinggroup can be provided. On the other hand, in a case where another numberis set in a storage position of the group destination number or thegroup specifying number, since it is different from the first parameter130 or the third parameter 132, the EMM data 108 will not be output fromthe output unit 107.

(3) Broadcasting for all Receivers

Assume that the number for specifying all receivers “0001h” is set inthe first field 110 of the EMM data 108 (see FIG. 4). Also assume thatthe fourth parameter 133 “0001h” is set in the parameter storage unit105 of each of the data selecting apparatuses 104 of all receivers 102in the digital communication system 100.

When the EMM data 108 is input to the data selecting apparatus 104, theinformation stored in the first field 110 is compared to the firstparameter 130, the second parameter 131, and the fourth parameters 133and 134 as already described with reference to FIG. 7. Since the numberfor specifying all receivers “0001h” is set in the first field 110 ofthe EMM data, this “0001h” matches the fourth parameter 133 of thereceiver 102, so that the EMM data 108 passes through the fourthdetecting circuit 138 to the output unit 107, which outputs the EMM data108. Thus, broadcasting for all receivers can be provided. On the otherhand, in a case where another number is set in a storage position of thenumber for specifying all receivers, since it is different from thefourth parameter 133, the EMM data 108 will not be output from theoutput unit 107.

(4) Broadcasting for Special Receiving Group

Assume that a special group number “0002h” is set in the first field 110of the EMM data 108 (see FIG. 5). Also assume that the fourth parameter134 “0002h” is set in the parameter storage unit 105 of the dataselecting apparatus 104 of each of all receivers 102 in the specialgroup.

When the EMM data 108 is input to the data selecting apparatus 104, theinformation stored in the first field 110 is compared to the firstparameter 130, the second parameter 131, and the fourth parameters 133and 134 as already described with reference to FIG. 7. Since the specialgroup number “0002h” is set in the first field 110, this “0002h” matchesthe fourth parameter 134 of the receiver 102, so that the EMM data 108passes through the fourth detecting circuit 139 to the output unit 107,which outputs the EMM data 108.

As thus described, broadcasting for the special group, namely, areceiving group comprising receivers under a contract of special servicecan be provided. On the other hand, in a case where another number isset in a storage position of the special group number, since it isdifferent from the fourth parameter 134, the EMM data 108 will not beoutput from the output unit 107.

Although the aforementioned four cases (broadcasting for the specifiedreceiver individually, broadcasting for the specified receiving groupfor each receiving group, broadcasting for all receivers, andbroadcasting for the special group) have been described as beingseparate, both data of the broadcasting for all receivers and thebroadcasting for the special group can be received provided that both“0001h” and “0002h” are set in the receiver 102 as the fourthparameters. Furthermore, the numbers of the fourth parameters and thefourth detecting circuits may be increased and plural kinds of specialgroups are set and detected, whereby data of broadcasting for pluralspecial groups can be received.

Besides, the information of the first field 110 or the receiver uniquenumber is illustrative and not restrictive. In addition, although theEMM data 108 is transmitted in a section data format in the abovedescription, a data selecting apparatus which is capable of selectingdata having another format may be employed. Further, although the datatransmission in digital broadcasting according to MPEG system standardhas been described, the data transmission is not restricted thereto, andis applicable to a case where data comprising plural fields is selected.

As should be appreciated from the foregoing description, in accordancewith the preferred embodiment of the present invention, in digitalbroadcasting in which various types of data is multiplexed andtransmitted, it is possible to realize the followings: i) Data is sentto receivers to which data is to be transmitted ii) Data is sent to thewhole receiving group obtained by grouping receivers by their individualnumbers iii) The same data is sent to all receivers simultaneously iv)Data is sent to all receivers which belong to each of groups obtained bygrouping receivers on a service basis according to contract ofbroadcasting service. As a consequence, destination can be specifiedflexibly in the data transmission, whereby the number of times oftransmission of the same data is significantly reduced and efficiency inthe use of the transmission bandwidth is greatly improved, as comparedwith a case where data is transmitted only to one receiver.

Furthermore, in accordance with the preferred embodiment of the presentinvention, since the receiver unique number for identifying thedestination receiver of the EMM data is composed of the group specifyinginformation indicating the receiving group to which the destinationreceiver belongs and the in-group identification information foridentifying the receiver in the receiving group, and the in-groupidentification information is included in the group destinationdirecting information of the EMM data, it is possible to make a decisionon the group destination directing information, and simultaneously onwhether there is a match of the in-group identification information.Therefore, when the EMM data is selected by the data selecting circuit,the match of the group specifying information is detected by a singledetecting circuit (third detecting circuit) irrespective of groupdestination or individual receiver destination, resulting in reducedamount of processing required for deciding whether to receive the EMMdata. As a consequence, the EMM data can be selected with a small scalecircuit.

INDUSTRIAL AVAILABILITY

Using the digital communication system, the transmitter, and the dataselecting apparatus of the present invention, data is sent to specifiedreceivers, and all receivers or prescribed receiving groupssimultaneously, which can improve degree of freedom with which datadestination is specified and achieve efficiency in the data transmissionbandwidth.

What is claimed is:
 1. A digital communication system comprising: atransmitter operable to sequentially transmit predetermined format data;and a plurality of receivers each including a data selecting apparatusoperable to select required data from received data group and to outputselected data, wherein said transmitter is further operable to transmitdata to said receivers in one of a first transmission mode, and a secondtransmission mode and a third transmission mode, wherein in the firsttransmission mode, group destination assignment information indicatingwhether the data is transmitted to a specified receiver of saidplurality of receivers, to a group consisting of specified pluralreceivers, or to all receivers, group specifying information forspecifying a receiving group of receiving groups to which the data is tobe transmitted, and in-group identification information for identifyinga receiver to which the data is transmitted, in a receiving group whichis specified by the group specifying information, are included in thedata, and the group destination assignment information in the firsttransmission mode indicates that the data is transmitted to a specifiedreceiver of said plurality of receivers, wherein in the secondtransmission mode, the group destination assignment information and thegroup specifying information are included in the data, and the groupdestination assignment information and the group specifying informationin the second transmission mode indicates that the data is transmittedto a group consisting of specified plural receivers, wherein in thethird transmission mode, the group destination assignment information isincluded in the data, and the group destination assignment informationin the third transmission mode indicates that the data is transmitted toall receivers or to a group consisting of plural receivers which arespecified by the group destination assignment information, wherein saidtransmitter includes data structuring means for structuring data to betransmitted, wherein said data selecting apparatus includes: parameterstorage means for prestoring plural parameters which are to be comparedto the group destination assignment information, the in-group,identification information, and the group specifying information:correspondence pattern detecting means for comparing the informationstored in the data to the parameters, respectively to detectcorrespondence patterns; and output means for selecting the requireddata according to the correspondence patterns detected by thecorrespondence pattern detecting means and outputting the selected data,wherein the group destination assignment information includes a groupdestination number indicating that the second transmission mode is usedto be transmitted when the data to be transmitted is destined for thegroup, wherein the group destination assignment information includes aspecified receiver destination number indicating that the firsttransmission mode is used to be transmitted when the data to betransmitted is destined for the specified receiver, wherein saidparameter storage means is operable to prestore a first parameter to becompared to the group destination number, a second parameter to becompared to the specified receiver destination number and the in-groupidentification information, and a third parameter to be compared to thegroup specifying information, wherein said correspondence patterndetecting means is operable to: detect transmission being performed inthe first transmission mode and indicating that the transmitted in-groupidentification information is a data to be received, when the specifiedreceiver destination number and the in-group identification informationmatch the second parameter; judge that the first correspondence patternis detected, when the group specifying information matches the thirdparameter in the first transmission mode; detect transmission beingperformed in the second transmission mode, when the group destinationnumber matches the first parameter; and judge that the secondcorrespondence pattern is detected, when the group specifyinginformation matches the third parameter, and wherein said output meansis operable to select the required data according to one of the firstand second correspondence patterns and outputs the selected data.
 2. Thedigital communication system of claim 1, wherein the group destinationassignment information includes all specifying numbers indicating thatthe third transmission mode is used to be transmitted when the data tobe transmitted is destined for the all receivers, wherein said parameterstorage means is further operable to prestore a fourth parameter to becompared to the all specifying numbers wherein said correspondencepattern detecting means is further operable to detect transmission beingperformed in the third transmission mode and to judge that being a datato be received, when detecting a third correspondence pattern that thenumber for specifying all receivers matches the fourth parameter in thethird transmission mode, and wherein said output means is furtheroperable to select the required data according to the thirdcorrespondence pattern and to output the selected data.
 3. The digitalcommunication system of claim 2, wherein group destination assignmentinformation includes a special group number when the data to betransmitted is destined for all receivers which belong to a specialgroup, when the data to be transmitted is destined for all receiverswhich belong to the special group, wherein said parameter storage meansis further operable to prestore a fourth parameter to be compared to thespecial group number, wherein said correspondence pattern detectingmeans is further operable to detect transmission being performed in thethird transmission mode and to judge that the special group number is adata to be received, when detecting a fourth correspondence pattern thatthe special group number matches the fourth parameter in the thirdtransmission mode, and wherein said output means is further operable toselect the required data according to the fourth correspondence patternand to output the selected data.
 4. A data selecting apparatus adaptedto be incorporated in a receiver in a digital communication system,which is operable to be supplied with predetermined format data asinputs and is operable to select required data from input data group andto output selected data said apparatus comprising: parameter storagemeans for presetoring plural parameters which are to be compared togroup destination assignment information in the data indicating whetherthe data to be transmitted is transmitted to a specified receiver ofsaid plurality of receivers, to a group consisting of specified pluralreceivers or to all receivers, group specifying information in the datafor specifying a receiving group of receiving groups to which the datais transmitted, and in-group identification information in the data foridentifying a receiver to which the data is to be transmitted, in areceiving group which is specified by the group specifying information;correspondence pattern detecting means for comparing the informationstored in the data to the parameters, respectively, to detectcorrespondence patterns; and output means for selecting the requireddata according to the correspondence patterns detected by saidcorrespondence pattern detecting means and outputting the selected data,and wherein the group destination assignment information includes agroup destination number indicating that the second transmission mode isused to be transmitted when the data to be transmitted is destined forthe group, wherein the group destination assignment information includesa specified receiver destination number indicating that the firsttransmission mode is used to be transmitted when the data to betransmitted is destined for the specified receiver, wherein saidparameter storage means is operable to prestore a first parameter to becompared to the group destination number, a second parameter to becompared to the specified receiver destination number and the in-groupidentification information, and a third parameter to be compared to thegroup specifying information, wherein said correspondence patterndetecting means is operable to: detect transmission being performed inthe first transmission mode and indicating that the transmitted in-groupidentification information is a data to be received, when the specifiedreceiver destination number and the in-group identification informationmatch the second parameter; judge that the first correspondence patternis detected, when the group specifying information matches the thirdparameter; to detect transmission being performed in the secondtransmission mode, when the group destination number matches the firstparameter; and judge that the second correspondence pattern is detected,when the group specifying information matches the third parameter, andsaid output means is operable to select the required data according toone of the first and second correspondence patterns and to output theselected data.
 5. The data selecting apparatus of claim 4, wherein thegroup destination assignment information includes all specifying numbersindicating that the third transmission mode is used to be transmitted,when the data to be transmitted is destined for the all receivers,wherein said parameter storage means is further operable to prestore afourth parameter to be compared to the all specifying numbers, whereinsaid correspondence pattern detecting means is further operable todetect transmission being performed in the third transmission mode andto judge that being a data to be received, when detecting a thirdcorrespondence pattern that the number for specifying all receiversmatches the fourth parameter, and wherein said output means is furtheroperable to select the required data according to the thirdcorrespondence pattern and to output the selected data.
 6. The dataselecting apparatus of claim 4, wherein the group destination assignmentinformation includes a special group number indicating that the data tobe transmitted is destined for all receivers which belongs to a specialgroup, when the data to be transmitted is destined for the all receiverswhich belong to the special group, wherein said parameter storage meansis further operable to prestore a fourth parameter to be compared to thespecial group number, wherein said correspondence pattern detectingmeans is further operable to detect transmission being performed in thethird transmission mode and to judge that the special group number is adata to be received, when detecting a fourth correspondence pattern thatthe special group number matches the fourth parameter, and wherein saidoutput means is further operable to select the required data accordingto the fourth correspondence pattern and to output the selected data.